test_shutil contains a handy helper function called write_file(filename. contents). If *filename* is a tuple, os.path.join() is used to concatenate it to a path.

To be really useful, the resulting file name should be returned, so the user can work with it.

So instead of:
fn = os.path.join(x,y)
write_file(fn, 'contents')

I'd prefer:
fn = write_file((x,y), 'contents')

I have attached a simple patch that achieves this and also applied the resulting simplification to some of the tests.

Hm, I don’t think the patch makes the test easier to read or maintain.  As I wrote in the commit message for #12721:

> For simple open then read/write calls, I have left the usual idiom
> (with open + read/write), as it is short and readable enough.

In the current tests, sometimes os.path.join is called and the resulting name (e.g. src) is used to write contents and then as argument to a shutil function; I actually prefer that src paths are created right before dst and with similar code.

So I think I’ll reject this patch.

ok. it would have saved some LOC for me, but it's nothing essential of course.